High pressure transducer



April 5, 1960 J. E. WOODS HIGH PRESSURE TRANSDUCER 2 Filed Aug. 24, 1956INVENTOR. JOHN E. WODS 317%, Y 3 1 ATTORNEYS United States Patent HIGHPRESSURE TRANSDUCER John E. Woods, Cohasset, Mass, assignor to Standard-Thomson Corporation, Waltham, Mass., a corporation of DelawareApplication August 24, 1956, Serial No. 606,093

5 Claims. (Cl. 73-3684) The present invention relates generally tomechanical transducers for converting applied pressure to linealdisplacement of an actuator element. The invention in more particularlyconcerned with actuators of the general type including a body ofdeformable material of limited compressibility which deforms to impelthe actuator element under pressure applied through a diaphragm.

This invention comprises an improvement upon the actuator disclosed inmy copending application Serial No. 420,120, filed March 31, 1954. It isan important object of this invention to provide an assembly adapted towithstand the large internal pressures to which actuators of thisgeneral class are subjected in certain applications.

Essentially, actuators of this type are so constructed that the appliedpressure displaces a given volume of the deformable body through thediaphragm, and the output element, which may be a sliding pin forexample, moves through a sufficient distance to compensate for thisdisplaced volume. This permits the use of an actuator element or pin ofrelatively small diameter, for example one-eighth of an inch or less,since a given volume displacement produces greater lineal movement for apin of small cross-section than for one of larger cross-section.

It is obvious, of course, that some external means must be provided tooppose outward motion of the pin. In practice, it is found that theproduction of pin motion against this opposing force necessitates thegeneration of,

large pressures within the body of the actuator, these pressures rangingfrom several hundred pounds per square inch up to thousands of poundsper square inch depending upon the particular application. Thesepressures in turn necessitate the use of heavy construction for the bodyof the actuator, which may lead to increased cost and undesirable bulk.The bulk of the housing is undesirable, not only because of the spaceand material utilized, but also because it reduces the responsiveness ofthe device in those applications where it is intended to operate as afunction of ambient temperature conditions. This point will be morefully discussed below.

For the foregoing reasons, it is a further object of the invention toprovide an assembly that can be easily and cheaply fabricated, while yetwithstanding the high pressures indicated above.

Another object is to provide an assembly having small bulk andrelatively thin walls to increase the responsiveness of the actuator toambient temperature conditions where this is desired.

With the above and other objects in view, the principal feature of thisinvention comprises an assembly including a housing defining a chamberhaving a pair of substantially hemispherical walls, and a supportsecured in an opening in the chamber, the support having a sleevebearing and an outwardly-flared portion within the chamber which isclosed by a metal diaphragm, and within which the deformable impellerbody is assembled. By this arrangement, there is provided an extremelyrigid assembly wherein the pressure forces are so distributed that ahousing of minimum wall thickness may be provided, and wherein a largepart of the assembly is situated within the chamber in a position ofrespose under the applied pressures.

Another feature of the invention resides in the ability of the device torespond rapidly to changes in the ambient temperature, while yet havingsuflicient strength to withstand the large applied pressures.

Another feature resides in the adaptability of the as sembly toconnection with a capillary for remote control.

Other features of the invention reside in certain features ofconstruction, assembly and modes of operation that will become evidentfrom a consideration of the following description of a preferedembodiment thereof, having reference to the appended drawing.

Referring to the drawing, there is provided a housing 12 which includesa pair of substantially hemispherical por' tions 14 and 16, the portions14 and 16 being mutually disposed to define a substantially sphericalchamber 18. The portions 14 and 16 are provided with outwardly extendingflanges 20 and 22, respectively, the flange 22 being preferably widerthan the flange 20 and being provided with mounting holes or othersuitable means, not shown, for mounting the actuator housing in relationto the device to be controlled.

The portion 16 of the housing has an opening to which is soldered an endof a capillary 24 extending to a thermal bulb 26 remote from the housing12. The bulb 26 is filled with a thermal liquid that communicates viathe capillary within the chamber 18. The chamber 18, the capillary 24and the bulb 26 are entirely filled with a thermal liquid.

The portion 14 of the housing is provided with an opening into which isreceived a support member 28, the member 28 having a cylindrical portionand a generally conical flared portion terminated by a shoulder 30 and aflange 32. The support 28 is perforated within the chamber 18 by one ormore holes 34 intermediate the shoulder 30 and the flange 32. Thehousing portions 14 and 16 and the support 28 are securely joined by anysuitable means that will form an hermetic seal, for example, resistancewelding, or brazing as indicated at 36.

A thin-walled flexible imperforate metal diaphragm 38, having an annularrim portion 40 adapted to fit within the shoulder 30 in the support 28,is soldered, welded, or brazed to the support 28 as indicated at 42.

It will thus be observed that the chamber 18 is hermetically sealed andentirely filled with thermal liquid except within the space defined bythe support 28 and the diaphragm 38. l

A pair of concentric sleeves 44 and 46, having inner end surfacecurvatures identical with the curvature of the flared portion of thesupport 28, are received in the latter and welded or brazed to thehousing 12 as indicated at 48. A rigid, cylindrical metal pin 50 isslidably received within the sleeve 44.

Between the diaphragm 38 and the pin 50 there is inserted a body 52 ofdeformable material having limited compressibility, for example rubberor a rubber substitute as described in said copending application.Between the body 52 and the pin 50 is inserted a wafer 54 adapted toprevent the body 52 from extruding out of the housing around the sidesof the actuator pin 50. A suitable material for the wafer 54 is Teflon,which is a trademark designating a polymer or co-polymer oftetrafluoroethylene.

The device is preferably assembled as follows. First, the diaphragm 38is assembled within the shoulder 30 of the support 28 and sealed theretoas indicated at 42. Next, the support 28 is received within the hole inthe hemispherical portion 14 of the housing with the flange 32 restingupon the flange 20. Next, the hemispherical portion 16 of the housing isassembled with its flange v.22 in contact with the flange 32. The threeflanges are then secured together as indicated at 36.

Next, the body 52 is received within the support, an operation whichisfacilitated 'bythe fact that the throat OrJcyIindr-ical portion of thesupport is of relatively large diameter. After the body 52 is iniplac'e,thesleeves 46 and 44 are assembled as shown in the drawing and securedto thehousing as indicated at 48. The Teflon insert Sound the pin 50 arethen received within the sleeve 44. Finally, the capillary 24.is securedto the opening in the hemispherical portion 16 of thehousing.

.The assembly is filled with thermal liquid in a conventional manner bymeans of a filling tube 56 at one end of the bulb 26 or in any othersuitable location. The method of filling is fully describedin saidcopending application. After filling, the tube 56 is crimped and sealedby soldering or brazing asindicated at 58.

ln'operation, the changes of temperature experienced by the thermalliquid in the bulb 26 cause changes of pressure within the chamber 18.Increasing pressure causes upward deflection of the diaphragm 3S, andsince the body 52 is closely confined its upper portion urges the pinoutwardly. The volume displaced by the pin in this motion is equal tothe volume displaced by the diaphragm 38, less a small amount resultingfrom slight compression of the body 52. It will be understood that thebody 52 has limited compressibility and most of the volume displacementgoes toward producingpinmotion.

The holes 34 in the support 28 allow the-liquid fill to surround theportion of the support within the chamber. Also, by reason of theflexibility of the diaphragm $8, the'p-ressure within the body 52substantially equals the pressure of the liquid fill surrounding thesupport.-

Hence, the pressures against the-innerand outer walls of the diaphragmand the flared portion-of the support 28 are equal. These .parts,therefore, are in repose at all p.r.essures.

Also, thewalls of the chamber 18, being ofspherical shape, provide theoptimum resistance to internalpressure for a given volume of fill andwall thickness. This same advantage may be achieved, but to a somewhatlesser degree, with a housing 'having a cylindrical wall withhemispherical ends, if desired.

The spherical shape of the-housing, which reduces the minimum wallthickness necessary to resist a certain maximum applied pressure, notonly permits a reduction in weight and bulk of the device but alsoprovides the optimum rate of transfer of heat through the wall from thesurroundings to the liquid fill within thechamber 18. For this reason,the device as illustrated can be made ambient ten'lperature-sensitive.Such a device is useful either with or without remote control, accordingto the application. As illustrated in the drawing, the device issensitive both to ambient temperature "and to the remote temperature atthe bulb 2.6. (Insulation around the housing may be used to reduceorsubstantially elimimate the sensitivity to ambient conditions at theactuator, if desired.) According to a modification of the device, theopening in the lower portion 16 of the housing is used for fillingpurposes only, and is not connected with a remote bulb. In this case,the device responds solely to ambient temperature conditions and may beused as a thermostat.

It will be understood that in any case the pin 50 is used to move anexternal device, not shown. This ma be, 'for example, a switch lever,toggle or the like, that is adapted to provide resilient resistance tooutward mo tion of the pin.

it will be further understood that while the invention has beendescribed with referencp to -a preferred embodiment thereof for purposesof illustration, variations from the form illustrated and described maybe accomplished for purposes of adapting the device to particularapplicaticns, :in accordance with techniques familiar "to those iskilled in this art, without departing irorn the spirit or scope of theinvention.

Having thus described the invention, I claim:

1. An actuator having, in combination, a housing including a pair ofsubstantially hemispherical portions mutually disposed to define asubstantially spherical chamber, the housing having an openingcommunicating with the chamber, a hollow support having a sleeve bearingsecured in said opening, the support having an outwardly flared portionwithin the chamber of greater inner diameter than said bearing, saidflared portion terminating in a flange secured at its periphery betweenthe adjacent edges of said hemispherical portions of the housing, theflange having a perforation within the chamber, a flexible metaldiaphragm enclosing said flared portion with said perforation externalthereto, a thermal liquid filling the entire space in said chamberexternal to saiddiaphragm and support, an actuator element slidablyreceived 'in said bearing, and a deformable body of limitedcompressibility contained within said flared portion of the support andbearing upon said element.

2., An actuator having, in combination, a housing including a pair ofsubstantially hemispherical portions mutually disposed to define asubstantially spherical chamber, each of said portions having an openingcommunicating with the chamber, a hollow support having a sleeve bearingsecured .in one of said openings, the support having an outwardly flaredportion Within the chamber of greater inner diameter than said bearing,said flared portion terminating in a flange secured at its peripherybetween the adjacent edges of saidhemispherical :portions of thehousing, the flange having a perforation within the chamber, a flexiblemetal diaphragm enclosing said flared portion with said perforationexternal thereto, a capillary communicating with the other ofsaid-openings and extending to a point remote from said housing, athermal liquid filling said capillary and the entire space in thechamber external to said diaphragm and support, an actuator elementslidably received in said bearing, and a deformable body of limitedcompressibility contained within said flared portion of the'support andbearing upon said element.

3. Anactuator having, in combination, a housing consisting of aplurality of members assembled to define a substantially sphericalchamber, the housing having an opening communicating with the chamber, ahollow sup- .port having a sleeve bearing secured in said opening, thesupport having an outwardly flared portion within the chamber of greaterinner diameter than said'bearing, said flared portion terminating in aflange secured at its periphery to the wall of the housing, the flangehaving perforation wi-thin the chamber, a flexible metal diaphragmenclosing said flared portion with said perforation external thereto, athermal liquid filling the entire space in said chamberjexternal to saiddiaphragm and support, an actuator element slidably received in saidbearing, and adeformable body of limited compressibility containedwithin said flared portion of the support and bearing upon said element.

4. An actuator having, in combination, a housing defining asubstantially spherical chamber and having an opening communicating withthe chamber, a hollow sup- .port sealed in said opening and having asleeve bearing and a portion extending into the chamber, said portionterminating in a flange secured at its periphery to the wall of thechamber, the flange having a perforation, a flexible inember closingsaid portion with the perforation external thereto, a thermal materialfilling theentire space in said chamber external to said flexible memberand support, an actuator element slidably received in said bearing, anda deformable body of limited com .pressibility contained within saidportion of the support and bearing :uponcsaid element.

5:. Factuator having, in combination, ah'ousin'g de= lining. asubstantially spherical chamber and having an 3 opening communicatingwith the chamber, a hollowsupport hermetically sealed by metallic fusionin said opening and having a sleeve bearing and a portion extending intothe chamber, a flexible metallic diaphragm member hermetically closingsaid portion by metallic fusion, 9.

References Cited in the file of this patent UNITED STATES PATENTSWheeler Nov. 15, 1887 Lawler Feb. 27, 1894 Swift Oct. 19, 1920 VernetApr. 26, 1938 FOREIGN PATENTS Great Britain Jan. 1, 1941

